Braking mechanism



March 30, 1937. c. v. CLARKE 2,075,176

BRAK ING MECHANISM Filed Dec. 20, 1934 3 Sheets Sheet l a a WWW March 30, 1937.

c. v. CLARKE 2,075,176

BRAKING MECHANISM led Dec. 20, 1934 3 Sheets-Sheet 2\ March 30, 1937. c. CLARKE BRAKING MECHANI SM 5 Sheets-Sheet 5 Filed Dec. 20, 1934 \&

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Patented Mar. 30, 1937 UNITED STATES PATENT OFFICE Application December 20, 1934, Serial No. 758,492

In Great Britain December 21, 1933 11 Claims.

mechanism for a self-propelled vehicle comprises brakingmembers arranged for actuation through a hydraulic transmission system, a device for feeding liquid to thesystem, a servo device for actuation of the feeding device, a manually operable device for applying pressure to liquid in the system and adapted upon its initial movement to render the servo device operative, and means which are responsive to the manual efiort applied to the manually operable device and also to the efl'ort exerted by the servo device and operating to render the servo device inoperative when the two efiorts reach a predetermined relative value.

It is here to be observed that the term manually operable device is used in its broadest aspect and is intended to include a device whether hand or foot operated and. controlled by an operator.

The invention is illustrated in the accompanying drawings in which: t

Figure 1 is a diagrammatic view;

Figure 2 is a section partly in elevation of one form of construction; v

Figure 3 is a section partly in elevation of a modified arrangement; and

Figure 4 is a. detail view of a cam and associated parts.

I Referring to Figures 1 and 2, a foot pedal I02 is pivotally mounted on a'lever I03 which is itself mounted to rock on a fixed bracket I04. The pedal I02 is pivotally connected to a rod I05 which extends into a cylinder I06 having therein a ram I01 and this rod is also connected to a rod I08 pivotally connected to a floating lever I09. One end of this lever is connected by a link H to a lever I I I the rocking of which results in operating against a draw-01f spring H2, a clutch I I2 for transmitting drive from a shaft I00 forming part of the power transmission of the vehicle to a cam H3 adapted when driven against a return spring I I3 to rock a lever I I4, the cam being rocked (when clutched to the shaft I00) in one c direction or the other (depending upon the direction of rotation of the shaft I00) through a part of a rotation: this lever is connected by a link H4 to a lever H4 outside a liquid supply tank H6, the lever H4 being fast with a spindle I I4 which extends through the wall of the tank and has on its inner end-a lever H4 operating a ram H moving in a cylinder H5 contained in the liquid supply tank H6. Thus, the clutch I I2 constitutes a device for bringing into action a servo effect derived from the shaft I00, this servo action being utilized to drive the ram of the arrangement H5.

The other end of the, lever I09 abuts against a head H! which is biased by a spring H8 and is connected to a plunger H9 in a cylinder I20. This cylinder has a port controlled by a spring loaded valve I2I which, when opened, places the cylinder I into communication with a vent or exhaust pipe I22 which returns to the tank H6. The rod I2 I of this valve abuts against a plunger I23 which is placed through a passage I24 into communication with a chamber I25 having in it a spring loaded plunger I26: this plunger I26 is 0 provided with a cup I21 and with ports I28 the arrangement providing in efiect a non-return valve which allows liquid to pass from a pipe I29 and through the plunger I26 and prevents the reverse flow. This pipe I29 extends to the delivery side of the ram and cylinder arrangement H5 while the upper end of the chamber I25 (1. e. that end into which the passage I24 opens) is open to one end of the cylinder I06, the ram I01 in which is provided with a cup I30 and with ports I3I so that liquid can flow from the right hand end of the cylinder I06 and through the ports I3I and past the cup I30 into the left hand end of the cylinder. The left hand end of the cylinder I06 is provided with aport I32 opening into a chamber I33 which communicates with a pipe I35 extending to a ram and cylinder arrangement, I35 for operating the brake shoes I 35 it being understood that only one set of brake shoes is shown and that a set wouldbe provided for each wheel which is to be braked. The cylinder I06 is also provided with a port I36 which when the ram I0! is moved to the right into the position shown, places the left hand end of the cylinder I06 into communication with a chamber I31 having an outlet valve I38: this valve when opened places the chamber I31 into. communication with an exhaust pipe I38 and the valve is adapted to be held closed by a rod I39 connected through a diaphragm sealing device I40 to a rod I4I adapted to be engaged by the upper end of the lever I03.

In operation, when the parts are in the brake released position the valve I2I is closed and liquid is trapp d in the cylinder I20. When the 5 H2 and from the plunger II9 whichis held by the liquid trapped in ,the cylinder I20. This operation rocks the lever I03 and the upper end thereof presses on the rod HI and moves the valve I38 to its closed position. Continued movement of the pedal is now efiected about its pivotal connection to'the lever I03. This results in motion being transmitted through the rod I05, to the lever I09 and as the valve I2I is closed, the head II1 forms a stationary abutment for the lever I09 which thus rocks in an anti-clockwise direction about'the head H1. The motion of the lever I09 is transmitted through the link IIO to the lever III which engages the clutch and this in turn results in bringing the servo action into effect resulting in the cam II3 operating the lever II4 which in turn operates the ram and cylinder II5. Liquid is thus displaced through the pipe I29 and through the non-return plunger I26 to the chamber I25 and thence through the ram I01 to'the pipe I35 the operation resulting in causing sufflcient liquid to be.

now moves to the left and thus allows the lever I09 to move about the rod I08 in a clockwise direction so that the lever III is operated to move the clutch and to interrupt the servo action.

It will be seen that the initial movement of the pedal has resulted in causing, through a mechanical servo action, the filling of the system with liquid and that when the pressure generated by the servo action and the pressure ex- 45 erted by the operator on the pedal reach a predetermined ratio (these opposing pressures acting on the valve I 2|) the servo action is automatically interrupted.

If, by reason of increased efiort being applied 50 to the pedal I02 the ram I 01 is caused to move further down the cylinder I 06, the liquid pressure applied to the plunger I23 is reduced or destroyed and the valve I2I closes and enables the liquid in the cylinder I20 again to provide a 55 reaction point for the lever I09 so that the servo mechanism is again brought into operation until the pressure applied to the plunger I23 by the servo mechanism reaches the predetermined ratio with respect to the increased force exerted 60 on the pedal I02, whereupon the servo mechanism will be rendered inoperative as has been described.

When the pedal is released the parts and pressures return to their original condition, the pres- 65 sure return being efiected by the release of the outlet valve I38.

Figure 3 illustrates an arrangement which is in many respects similar to the arrangement described with reference to Figures 1 and 2 and 70 similar parts are indicated by similar numerals.

Firstly, in place of connecting the pipe I 35 to the tank II6 by a port I36 arranged to be uncovered by the ram I01, the pipe I35 is branched to a non-return valve I42 arranged to be opened 75 against the pressure of the liquid in the pipe I35 by a push rod I43 operated by a cam I 44 on the rod I05, this cam operating to open the valve when the ram I01 is at or near the end of its in-' stroke (i. e. at a time corresponding to the time at which the port I36 is uncovered by the ram I01 of Figures 1 and 2). It will be seen that when the valve is opened, the pipe I35 is opened to the chamber I31 controlled by the valve I38 which itself controls communications between this chamber and the tank, communication being efiected through the pipe I38.

The valve operating arrangement shown in Figure 3 (Le, the cams and push rods) avoids the necessity for the formation of ports in the cylinder of a ram having a rubber (or like) cup or other packing and hence avoids difficulties due to the tendency of such ports to score or tear the rubber cup, especially when the cup side of the ram is employed to generate pressure on the liquid. It is to be understood that the operation of a valve by a cam and push rod could be applied to the arrangement shown in Figure 1.

Secondly the non-return valve I21, I28 Figure 2 is placed on the supply tank side of .a device providing an artificial resiliency to the liquid contained in the chamber I31: the device comprises a ram I46 which is loaded by a spring I41 the ram moving in a cylinder I48 open to the pipe I29, this pipe being in unrestricted communication with the chamber I31: the cylinder I48 is also connected through a pipe I29 to a non-return valve I49 which performs the functions of the valves I21, I28 insofar as it prevents reversal of flow from the chamber I31 to the tank II6, the valve I49 opening direct to the cylinder I50 of the ram and cylinder arrangement I I operated by the lever I I4. As is shown, it is preferred to house the cylinder I48 within the tank 6. It will be seen that when the ram and cylinder arrangement H5 is operated by the lever II4, liquid is displaced from the tank IIS past the non-return valve I49 to the pipes I29, I29, the chamber I31 and thence through the ram I01 to the pipe I35: liquid is also displaced into the cylinder 8 and the ram I46 therein is moved against the reaction of the spring I41, the reaction being of course equal to the pressure of the liquid. Now when, after the servo action, the lever II 4 has filled the system with liquid and further braking efiort is transmitted through the liquid by the direct operation of the ram I01 by the pedal I02, the ram I01 will move very slightly in applying the increased pressure and without the provision .of the ram I 46 and spring I41 this slight movement would result in increasing the capacity of the system between the tank I I6 and the right hand iace of the ram I01 and thus would result in causing a pressure drop in this part of the system: the provision of the ram I45 and spring I41 in this part of the system, howevenprovides an artificial elasticity which enables the total capacity to be automatically varied to maintain a sensibly constant pressure, 1. e. if the pressure should tend to drop, the spring I41 would move the ram I46 to maintain the pressure by decreasing the capacity of the system. e

It will be seen that the invention provides for a minimum extent of movement of the brake pedal due to the fact that initial application of the brakes is effected by servo action which is merely controlled by the pedal. The quantity of liquid displaced by the servo action can be comparatively great and hence the arrangement,

would be of particular advantage for use on heavy vehicles and particularly public service vehicles such as trolley busses, inasmuch as it reduces the manual effort to a minimum.

What I claim is:

1. In braking mechanism for a self-propelled vehicle, the combination of braking members, a hydraulic transmission system, a device operating to feed liquid to the system a servo device operating to actuate the device, a manually operable device operating in its initial movement to render the servo device operative and also operating to apply pressure to liquid fed to the system, and means responsive to the effort applied to the manually operable device and also to the eflort exerted by the servo device, the said means operating to render the servo device inoperative when the said two efforts reach a predetermined relative value. v I

2. In braking mechanism for a self-propelled vehicle, the combination of braking members, a hydraulic transmission system, a device operating to feed liquid to the system, a servo device operating to actuate thedevice, a manually operable device operating in-its initial movement to applied by an operator to the manually operable device, and also to the pressure of liquid fed to the system by the feeding device, the said means rendering the servo device inoperative when the two pressures reach a predetermined relative value. r

3. In braking mechanism fora self-propelled vehicle, the combination of braking members, a hydraulic transmission system, a device operating to feed liquid to the system, a 'servo device operating to actuate the device, a manually operable device operating to apply pressure to the system, a floating member operatively associated with the manually operable device and with the servo device, and means responsive to the difference between the pressure exerted by the operator on the manually operated device and the pressure of liquid fed to the system by the feeding device, the said means providing, when the difference is at a maximum, a first reaction point for the floating member so that actuation of the manually operable member is transmitted to effect actuation of the servo device and when the difierence falls to a predetermined value the responsive device moves to allow the floating member to render the servo device inoperative. 4. An arrangement as claimed in claim 3 and in which the responsive means comprises a valve which is subjected on one side to the pressure of liquid which is trapped in a cylinder and re acts against a member against which the floating member reacts and on the other side to a pressure dependent on the pressure of liquid fed by the servo device to the system, the valve opening to allow the escape of liquid from the cylinder and hence allowing the member to move when the pressure on the said other side overcomes the reaction pressure of liquid within the cylinder. A

5. In braking mechanism for a self-propelled vehicle, the combination of braking members, a hydraulic transmission system, a first ram and cylinder device operating to feed liquid to the system, a servo device operating to actuate the device, a second ram and cylinder device operating to apply pressure to the system and in its initial movement to render the servo device operative, and means responsive to the effort transmitted to the second ram and cylinder device and also to the pressure of liquid fed by the first ram and cylinder device, the said means operating to render the servo device inoperative when the effort and pressure reach a predetersystem, a servo device operatingjto actuate the device, a second ram.and cylinder device operating to apply pressure to the system, a chamber containing liquid, a valve controlling the discharge of liquid from the chamber, a reaction member reacting against liquid in the chamber, a floating member reacting against the said reaction member, means connecting the floating member to the second ram and cylinder device and to the servo device, andme'ans applying to the valve'and externally of the chamber a pressure dependent upon that developed by the first ram and cylinder arrangement, whereby reaction for the floating member is first supplied by liquid in the chamber, this reactionenabling the second ram and cylinder device to operate through the floating member to render the servo device operative and when the pressure. developed by the first ram and cylinder device reaches a predetermined-value relative to the reaction pressure in the chamber, the valve iscaused to open and the floating member thereby allowed to move to render the servo device inoperative.

'7. In braking mechanism for a self-propelled vehicle, the combination of braking members, a hydraulic transmission system, a first ram and cylinder device operating to feed liquid to the system, a servo device operating to actuate the device, a second ram and cylinder device operating to apply pressure to the system, the second ram having passages through which liquid is fed by the first ram and cylinder arrangement, non-return valves in the passages and operating to prevent liquid from returning from the system through the said passages,' and in its initial movement to render the servo device operative, and means responsive to the effort transmitted to the second ram and cylinder device and also to the pressure of liquid fed by the first ram and cylinder device, the said means operating to render the servo device inoperative when the efiort and pressure reach a predetermined relative value.

8. In braking mechanism for a self-propelled vehicle, the combination of braking members, a hydraulic transmission system, .a first ram and cylinder device operating to feed liquid to the system, a servo device operating to actuate the device, a second ram and cylinder device operating to apply pressure to the system, the second ram having passages through which liquid is fed by the first ram and cylinder arrangement, nonreturn valves in the passages and operating to prevent liquid from returning from the system through the said passages, a chamber containing liquid, a valve controlling the discharge of liquid from the chamber, a reaction member reacting against liquid in the chamber, a floating member reacting against the said reaction member, means connecting the floating member to the second ram and cylinder device and to the servo device, and means applying to the valve and externally to the chamber a pressure dependent upon that developed by the first ram and cylinder arrange.-

ment, whereby reaction for the floating member is first supplied by liquid in the chamber, this reaction enabling the second'ram and Cylinder device to operate through the floating member to render the servo device operative and when the pressure developed by the first ram and cylinder device reaches a predetermined value relative to the reaction pressure in the chamber, the valve is caused to open and the floating member thereby allowed to move, to render the servo device inoperative.

9. In braking mechanism for a self-propelled vehicle and having a power transmission member, the combination of braking members, a hydraulic transmission system, a device operating to feed liquid to the system, a clutch device arranged to transmit power from the transmission member to the feeding device, a manually operable device operating in its initial movement to render the clutch device operative and also operating to apply pressure to liquid fed to the system, and means responsive to, the effort applied to the manually operable device and also to the effort transmitted through the clutch, the said means operating to render the clutch device inoperative when the said two efiorts reach a predetermined relative value.

10. In braking mechanism for a self-propelled vehicle and having a power transmission member, the combination of braking members, a hydraulic transmission system, a first ram and cylinder device operating to feed liquid to the system, a clutch device arranged to transmit power from the transmission member to the feeding device, a second ram and cylinder device operating to apply pressure to the system and in its initial movement to render the clutch device operative, and means responsive to the eflort transmitted to the second ram and cylinder device and also to the pressure of'liquid fed by the first ram and cylinder device, the said me ans operating to render the clutch device inoperative whendevice, ,a second ram and cylinder device operating to apply pressure to the system, a chamberv containing liquid, a valve controlling the discharge of liquid from the chamber, a reaction member reacting against liquid in the chamber, a floating member reacting against thevsaid reaction member, means connecting the floating member to the second ram and cylinder device and to the clutch device, and means applying to thevalve and externally of the chamber a pressure dependent upon thatdeveloped by the first ram and cylinder arrangement, whereby reac-' tion for the floating member is first supplied by liquid in the chamber, this reaction enabling the second ram and cylinder device to operate through the floating member to render the clutch device operative and when the pressure developed by the first ram and cylinder device reaches a predetermined value relative to the reaction pressure in the chamber, the valve is caused to open and the floating member thereby allowed to move to render theclutch device inoperative.

CECIL VANDEPEER CLARKE. 

